The prevention of pain is a critical component of medical practice, whether it is needed for the alleviation of endemic pain due to disease, injury, or other conditions, or to enable medical or surgical procedures. Among the variety of anesthetic methods currently used in modern medicine, some methods allow regional or local pain relief or numbness, either in absence or presence of patient sedation or consciousness. Peripheral nerve blocks may be used for nerves outside of the central nervous system, and find particular use in outpatient surgical settings. However, peripheral nerve blocks pose particular problems in terms of safety and effective duration; that is, drugs and dosages that are found to be effective and safe when applied to nerves of the central nervous system (e.g., during epidural injection) do not predictably have the same systemic toxicity, neurotoxicity, and effectiveness when applied to peripheral nerve blocks. Therefore, there is a need for safer, longer-lasting, and more effective anesthetic and analgesic compositions and methods for peripheral nerve blocks.